A conventional digital light processing (DLP) projector includes an illumination system, a digital micro-mirror device (DMD) and a projection lens. The illumination system is used to provide an illumination beam, the digital micro-mirror device is used to convert the illumination beam into an image beam, and the projection lens is used to project the image beam onto a screen to form an image screen on the screen. In addition, with the development of illumination technology, most of the conventional projectors have employed a laser source as the light source of the illumination system, wherein the laser source may be laser diode LD).
FIG. 1 is a schematic view of a conventional illumination system employing a laser source. Referring FIG. 1. In the illumination system 100, the laser source module 110 can emit a blue beam 112. The blue beam 112 is irradiated to the phosphor wheel 140 after sequentially passing through the collimating element 122, the dichroic mirror 130 and the lenses 123, 124. The phosphor wheel 140 rotates and may have a reflective portion, a green phosphor region, a yellow phosphor region and a transmissive region or an opening region (these elements of the phosphor wheel 140 are not shown), and the green phosphor region and the yellow phosphor region both are formed on the reflective portion.
When the blue beam 112 is individually irradiated in the green phosphor region and the yellow phosphor region, the green phosphor region and the yellow phosphor region respectively excite the green beam 113 and the yellow beam 114, and the reflective portion reflects the green beam 113 and the yellow beam 114 to the dichroic mirror 130. The green beam 113 and the light beam 114 reflected by the dichroic mirror 130 are irradiated to the rotatable color wheel 150 after passing through the lens 125. The opening region of the phosphor wheel 140 may allow the blue beam 112 to penetrate. After the blue beam 112 penetrating the opening region, the blue beam 112 sequentially passes through the lenses 126, 127, the reflective portions 161, 162, the lens 128, the reflective portion 163, the lens 129, the dichroic mirror 130 and the lens 150. Thereafter, the blue beam 112 is irradiated to the color wheel 150.
The color wheel 150 has a red light filter region, a green light filter region, a transparent region and a diffusion region. The yellow phosphor region corresponds to the red light filter region and the transparent region, the green phosphor region corresponds to the green light filter region, and the opening region corresponds to the diffusion region. The color wheel 150 and the phosphor wheel 140 can be rotated in cooperation with each other, so that the green beam 113 is irradiated to the green light filter region, the yellow beam 114 is irradiated to the red light filter region and the transparent region, and the blue beam 112 is irradiated to the diffusion region. The color beam filtered by the color wheel 150 is a blue, a green beam and a red beam for forming a color image and a yellow beam for increasing the luminance. The color beams then enter the optical integration rod 170.
However, according to the above description, it is understood that the conventional illumination system 100 requires many optical elements (e.g., a plurality of lenses 123 to 128) and has a complicated optical layout. Therefore, the conventional illumination system 100 has some disadvantages such as high cost, large volume and poor optical efficiency.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.